On a quiet afternoon in 1947, retired bank manager Oswald Gibson is shot in the head while fishing. In Scotland, a respectable family doctor is killed in the same manner - and with the same gun. What is the connection? Scotland Yard's Detective Inspector Billy Styles and local detective Vic Chivers are baffled until a letter from Gibson is discovered that may shed some light on the case - a letter concerning former Scotland Yard detective John Madden.